Transmission interlock



April 1939- w. B. HERNDON 2,153,085

TRANSMI SS ION INTERLOCK Filed July 15, 1938 Zhwentor Gttornegs Patented Apr. 4, 1939 UNITED STATES PATENT OFFICE TRANSMISSION INTERLOCK Application July 15, 1938, Serial No. 219,394

7 Claims.

This invention relates to change speed transmissions such as are used for motor vehicles and is particularly concerned with an improved detent and interlock for movable members which are used as parts of the mechanism by which changes in driving ratio are effected.

The object of the invention is to provide an improved detent and interlock whereby a selected mechanism is retained in position and whereby the unselected mechanism is restrained from movement from a neutral to an active position.

As further objects, the invention aims to accomplish its major object by a construction which shall be effective and comparatively simple and inexpensive.

In the drawing:

Figure 1 is a view in side elevation of a transmission housing, the wall being partly broken away, and showing parts in section.

Figure 2 is a section on line 2--2 of Figure 1.

Figure 3 is a view corresponding to Figure 1 but with certain parts displaced from the position shown by Figure 1.

On the drawing, numeral 1 represents a housing for the change speed mechanism of a motor vehicle. No invention is herein claimed for the gearing per se and it will be briefly referred to only. There is shown a gear 9 which is on the input shaft, the shaft driven by the engine through the conventional clutch. The output shaft marked H is splined with straight teeth not shown and with spiral teeth at l5. Between these teeth this output shaft carries rotatably mounted thereon a gear 11. Gear I1 is in constant mesh with a gear 19 on a countershaft, not shown, this countershaft being driven by the input shaft through the instrumentality of a train of gears of which gear 9 is the driving gear.

A clutch 35 is slidably mounted on the straight splines and is adapted to make clutch engagement with clutch teeth of the input member 9 for driving in direct or high speed. Preferably, and as shown in the drawing some conventional 45 synchronizing means will be used to effect synchronous rotation prior to engagement of the jaw teeth. This synchronizing mechanism is marked 23 on Figure 1. In a similar way clutch may be moved to the right whereupon a similar synchronizing means and jaw tooth engagement may be employed to lock gear H to the output shaft ll whereupon a drive in second speed is effected. For the purpose of reciprocating clutch 35 the gear housing journals a horizontally disposed rockshaft 21. Externally of the housing rockshaft 21 has a lever arm 29. Within the gear housing shaft 21 has a hub- 3| from which extends vertically upward an arm 33, this arm carrying a shoe or like device to engage an annulus on the sliding clutch 35. It will then be understood that rotating of the rockshaft 21 reciprocates clutch 35 in opposite directions from a neutral position to effect high speed or second speed.

Gear 3! slides on splines l5 in one direction from its neutral position to engage a countershaft gear for driving in low speed. It may reciprocate in the opposite direction to engage a gear on a shaft mounted parallel with the countershait and driven thereby. The latter position of gear 31 produces a drive in reverse. For the sliding of gear 31 there is used a second rockshaft 39, this rockshaft being also journaled in the side wall of the transmission and arranged in parallel relation to shaft 21. Rockshaft 39 has an external operating arm 4| and an inner lever arm 43 which latter extends upwardly from a hub 45 and carries a shoe 4'! which engages with a collar 49 associated with gear 31.

It is intended that the rockshafts 21 and 39 shall be selectively rotated by some remote control means, preferably in the form of a lever mounted on the steeding column adjacent the steering wheel. The connections between such remote control means and the lever arms 29 and 4| may be of any form found convenient for the purpose.

The invention sought to be protected by this application is more particularly related to the means for resiliently holding either rockshaft y;

and the associated gear and clutch positioning parts in a selected position and for preventing the movement of either one of such mechanisms from its neutral position when the other is in an active position. To this end there is provided a tube formation 5| which may be as shown in Figure 2 a passage in the housing wall. The axis of this passage intersects the inner ends of the rockshafts 21 and 39. Within the passage there is reciprocably mounted a tubular element which may preferably, but not necessarily, be formed from two parts 53 and 55, and within this tubular element is a coil spring 51. The remote ends of parts 53 and 55 are recessed to form pockets as at 59 to receive balls 6|. The pockets limit the inward movement of the balls whereby axial thrust against the ball may move the tubular member. The rockshaft hubs are provided with cams 63 and 63'. These cams have three recesses 65, 61, 69 and 65', 61' and 69.

The spring 51 presses the balls away from each other and into one or another of the recesses in the cams. It will be seen from Figure 1 that the resilient resistance of spring 51 must be overcome to rock either rockshaft from any one of its three positions. To so change the position of the rockshaft the ball must be lifted over a ledge H such ledges being provided between the adjacent recesses. It will be observed that the remote ends of each cam have shoulders I3 which are of greater radial distance from the center of rotation than are the ledges H. From Figure 1 it will be evident that in the inactive position of both shafts the tubular member 53-55 has its ends positioned adjacent the ledges 1| andthat the distance between ledges is in excess of the combined length of the parts 53 and 55. This makes possible the rocking of one shaft from its neutral to its active position, the parts mov ing from the position shown by Figure 1 to that illustrated in Figure 3. In the position of Figure 3 the tubular element is between a ledge ll on the unmoved cam of shaft 21 and a shoulder 13 on the cam of shaft 39 which has been rotated. Owing to the greater radial distance of shoulder 13 the linear distance between ledge H and shoulder 13 in the position of parts shown in Figure 3 corresponds substantially with the combined length of parts 53 and 55 so that the ends of the tubular element substantially engage both H and 13. In consequence the spring 57, acting upon the ball at the right end of the tubular member serves as a yielding means to hold one operative mechanism in its active position. At the same time the other mechanism, that related to rockshaft 21 is held from move ment from its neutral position by the engagement of the tubular member 53 and 55 with the ledges H on either side of the neutral recess. The device may also operate if the tubular member does not actually contact at H as well as at 13. If the contact does not occur at "H when the tubular member is reciprocated incidental to its contact at 13, the reciprocation is nevertheless suflicient to seat ball 6| in the bottom of the pocket 59 and thus prevent rotation of cam 63 with shaft 2'5.

The expedient above described is very simple and comparatively inexpensive and is effective in preventing the movement of one shift mechanism from neutral when the other is in active position.

I claim:

1. In a change speed transmission, spaced members adapted to be selectively moved to introduce driving ratios, each said member having a plurality of recesses with ledges therebetween and with shoulders at each end of each series of recesses, an interlock mounted for reciprocation between said members, the movement of said members being such that a line joining an intermediate recess of one of said members with any recess of the other may be made to coincide with the axis of said interlock, the length of the interlock being substantially less than a line parallel with said axis and extending between corre sponding ledges but approximately equal to a similar line between a ledge and a shoulder.

2. The invention defined by claim 1, said interlock being tubular,- balls in the ends of said tubular interlock and a spring between said balls.

3. The invention defined by claim 1, said interlock being tubular and having recesses at its ends, balls in said recesses adapted to seat therein and reciprocate said interlock in response to a movement of one of said members whereby the end of said interlockis' moved away from the ledges of the member being moved.

4. The invention defined by claim 1, said transmission being positioned in a gear housing, said gear housing having a tubular journal for said interlock within a wall thereof.

5. The inventiondefined by claim 1, said interlock being composed of a plurality of axially disposed tubes.

6. The invention defined by claim 1, said members being parallel rockshafts, said rockshafts provided with cams, and said recesses, ledges and. shoulders being formed on said cams.

7. In a change speed transmission, spaced members adapted to be selectively moved to introduce driving ratios, each said member having a plurality of recesses with ledges therebetween and with shoulders at each end of each series of recesses, an interlock mounted for reciprocation between said members, the movement of said members being such that a line joining an intermediate recess of one of said members with any recess of the other may be made to coincide with the axis of said interlock, the interlock being tubular and having shouldered pockets within its 

